This invention relates to crimped elements of the kind that may be used in cigarettes and related products, for example as tobacco smoke filters. The invention further relates to methods and apparatus for the manufacture of such elements.
Continuous rod-like members, particularly those to be used as cigarette filters, are commonly formed from tows of fibrous filter material, for example, plasticized cellulose acetate, or may alternatively be formed from gathered plastic film or paper or other materials that can be formed by well-known techniques into air-pervious plugs with a multiplicity of intercommunicating interstices which define a tortuous path for smoke, or a mixture of smoke and air, passing therethrough. In the case of a tow, the filamentary material is processed by various means as the tow travels lengthwise, through a continuous processing line. Depending on whether the processed material is self-sustaining or not, it may be continuously wrapped and cut into discrete lengths which may be further subdivided to form individual elements for association with tobacco sections in the production of filtered cigarettes.
It is common in continuously processing polymeric materials such as cellulose acetate tow or the like to provide spaced, radially compressed or crimped, sections. It is well known in the art to form successive, longitudinally spaced, crimped sections in a travelling length of suck materials by the use of a crimping apparatus comprising, for example, one or more crimping wheels which rotate in the direction of travel of the material and which may have spaced teeth or lobes about their periphery which successively engage the material to squeeze and compress the same at spaced intervals along its length. A plurality of crimping wheels may be positioned around the path of travel of the material with the rotation of the wheels synchronized such that teeth from multiple wheels simultaneously engage the material from different sides. Thus, as respective sets of teeth from the wheels synchronously move into engagement with the material, the material is squeezed and compressed therebetween forming a crimped section of smaller or, at least different, cross-section. As the teeth move out of engagement with the material, the original cross-section of the material is maintained. When the next set of teeth engages the material a further crimped section is formed and so on.
Examples of known crimping wheel structures used in the manufacture of cigarette filter rods and the like are disclosed in U.S. Pat. Nos. 3,826,177 and 4,085,663, commonly assigned with the instant application. The disclosures of these patents are expressly incorporated herein in their entirety by reference.
In known crimping wheel structures using a plurality of wheels, there are small gaps between the edges of the respective wheels. Therefore, as the travelling crimpable material passes between the wheels, commonly in a heated state, it is crimped, and edge portions of the material may be squeezed through such gaps at the interface between juxtaposed crimping teeth, resulting in the formation of "flashing" or thin fins on the edges of the compressed or crimped sections of the finished product. Such flashing is, at best, unsightly and undesirable in most applications; yet, in some applications, any substantial flashing is totally unacceptable.